I'll contribute to the current flood of EclipseCon slides by posting mine as well! They aren't in the best shape because of the conversion they went through but have a look anyway.
Those are the slides of the talk "An Early Adopter's Retrospective on an E4 instrual app", and you can read more, including the abstract, on the EclipseCon website. I hope you can infer the missing bits from simply reading the slides...
The EclipseCon ended almost two weeks ago already, so I had some time to recover and order my thoughts. To me, the best part was definitely meeting people from the Eclipse and OSGi communities (thanks to the OSGi DevCon being held at the same time and place), discussing various topics and meeting the creators of the projects I'm using. For various reasons, I did not meet everyone I hoped I would, but I'd say I scored a solid 80% :-).
I also had the occasion to chat with some developers of the E4 team about the future of the application platform and some ideas I have about improving the "OSGi experience". Mails are ideal for very technical details (it's easier to type code than to pronounce it :-)) but discussions about the general architecture benefit greatly from face to face meetings.
So, thanks to everyone I chatted with, it was a real pleasure. I came back from California with a project in my to-do list and much more in my mind. All in all, it was an interesting experience.